In the project shown below, activities are represented by arrows, and the number for each activity also

Question:

In the project shown below, activities are represented by arrows, and the number for each activity also indicates its normal duration (in days).
a) Determine the critical path and the length of this project.
b) Assume that each activity, except 1 and 2, can be crashed up to 2 days at a cost equal to the activity number. E.g. activity 6 normally takes 6 days, but could be crashed to 5 days for a cost of $6, or to 4 days for a total of $12. Determine the least-cost 26-day schedule. Show the activities that are crashed and the total crash costs.